A closure selectively closes an access port on a pressure-containing vessel, providing access to its interior. Various designs of quick acting closures are utilized on pressure vessels, including pipelines, within the chemical, oil and gas, food, and nuclear industries. The demand to frequently obtain access to pressure vessels has been increasing, thereby enhancing the need for a safe closure that provides quick opening and closing/sealing capabilities.
Closure designs commonly fall into one of three groups: threaded style, clamp style, or flat door. Each style has three basic parts: a hub section (e.g. a female connector or housing) permanently and sealingly secured to the vessel or pipeline, a plug (e.g. a male connector or a plug) which provides a seal against the hub, and a plug hinge or plug transport mechanism.
The flat door version offers the quickest access of the three types. Yet, its weight makes installation difficult, and corrosion over long periods can inhibit operation. Elaborate sealing techniques are also required. The flat door is usually secured to the hub with a self-hinging or lifting arrangement.
The clamp style closure functions by bringing two flanges together and then securing their position with an external annular locking ring arrangement. Commonly, the annular lock ring is presented in two segments, which may be held together via a bolting arrangement. While the concept is simple, the closure assembly is heavy, and difficult to operate and seal. Not only does the door require some handling/articulation to the permanent portion of the closure, but also the locking ring itself poses handling difficulties. Some type of powered drive is commonly required to secure such a device. One major inhibition is that the presence of pressure is not obvious to the operator. Cases of catastrophic failure and doors being opened under operating pressure have resulted in death and injury.
The flat door and the clamp style flanges are complex, difficult to manufacture and operate, and/or require removal of material from critical pressure retaining surfaces that prevent compliance with international design codes. Some of these prior art designs do not or cannot incorporate an integral safety locking feature that prevents unsafe handling and operation of the closure.
A frequent application for a closure is on pipelines to launch and retrieve a “pig,” which is a device used in cleaning and inspecting the pipelines. Historically, most operations have used a working pressure below 5000 psi. Recently, sectors of the petroleum industry, including pig-launching pipelines, are requiring the use of higher-pressure closures.
Performing maintenance on closure assemblies is difficult and expensive. A need therefore exists for a closure assembly having a simple and reliable design that is not susceptible to contamination, is easy to maintain, and provides the ability to reliably and securely close a pipe, a pressure vessel, or other container.
Furthermore, there is a need for a closure assembly that can quickly and easily provide access to the interior of a pipe, a pressure vessel, or other container.
Although a number of different closures are in use, few of them, if any, are designed for operation at high-pressure levels more frequently demanded by the petroleum industry. Therefore, a need also exists for a closure assembly that can repeatedly, reliably, and safely seal a pipe, a pressure vessel, or other container comprising fluids at high pressures.
Other embodiments of male and female fluid connectors can be used to transfer fluid between two vessels, containers, pipes, or fluid conduits. Specifically, in constructing a pipe assembly, the ends of two pieces of pipe are joined axially to form a single conduit that is used to transport materials from one point to another. Often times, the materials being transported are fluid or gaseous in nature, and, particularly in those circumstances, it is desired that the pipeline be impervious to leaks. In order to accomplish that goal, those skilled in the business of pipe and pipeline construction are constantly in search of improved means for securing the joints formed by connecting the ends of pipe together.
There are numerous methods currently in use by those in the pipe and pipeline construction industry to obtain a secure joint. These methods employ different types of components and can be distinguished by the various ways in which such components are employed. The selection of these different methods will usually depend on the overall design requirements of the pipeline. For example, one important design requirement exists when it is desired that the pipe joints be sealed such that the material being transported within the pipeline cannot escape and, conversely, foreign materials are prevented from entering the pipeline.
Another important design requirement exists when it becomes necessary to join the pipe components in a rigid or restrained manner. This is usually desired in order to prevent the pipe components from separating due to thrust forces that often occur when the piping system is subjected to internal pressure or when earth tremors or other external forces contact the pipes. Still another objective is to make assembly of the pipe joints as simple, economical and reliable as possible.
One current method for connecting pipe together employs the use of flanged fittings and gaskets. These are typical components in rigid piping systems, particularly aboveground systems, such as water filtration plants, sewage disposal plants, wastewater treatment plants, pumping stations, chemical plants, and refineries. Often times, the flanged fitting is threaded directly onto the pipe. This is accomplished by threading an end of a pipe and threading a compatibly sized flanged fitting. The threaded flanged fitting is then machine-tightened onto the end of the pipe and transported to the field in this joined condition. The threaded flanged pipe is then connected to another flanged pipe, usually by bolting means. In order to obtain a leak-free joint, a gasket may be used between the faces of the two-flanged fittings.
The use of threaded flanged fittings presents several limitations. Specifically, the threaded flanged fitting is custom machined to accommodate the exact diameter of the pipe and to provide a smooth surface across the end of the pipe and the face of the flanged fitting. In addition, extremely high torques is required to tighten properly the flanged fitting onto the threaded pipe. Consequently, one major limitation of this system is that preparation of the flanged fitting and pipe requires sophisticated machinery not usually available on-site where the finished component will be assembled and installed.
A further problem with flanged fittings is that the time taken to tighten a large number of flange bolts to the torque, necessary to achieve a good seal between the pipe, gasket and seal, can be considerable. It would therefore be advantageous if the use of flange bolts could be eliminated and the torque needed to achieve an efficient seal reduced without any loss of seal integrity.
Another common method for connecting the ends of pipe involves inserting the spigot end of one pipe into the expanded end of a second pipe, the interior profile of which has been specially fabricated to form a socket (the expanded end sometimes being referred to as the “bell end”). The bell end is sized to accommodate the spigot end of the pipe to be received. The connection obtained by this method is also known in the industry as a “push-on joint.” There are several methods used to seal and/or secure the push-on joint. One such method involves inserting a fitted gasket within an annular recess formed within the throat of the socket of the bell. After the gasket is inserted into the annular recess of the socket, the spigot is aligned and forced through the gasket into the bottom of the socket, thereby compressing the gasket and sealing the two pipe ends together.
Still another common method for connecting pipe is sometimes referred to as a “mechanical joint.” In embodiments of this method, the bell end of a pipe has a flanged portion cast on it. The spigot end of a second pipe is fitted with a slidable gland fitting and a gasket, which is conically shaped such that one face of the gasket is diametrically larger than the second face of the gasket. The conically shaped gasket is positioned between the gland fitting and the spigot end of the pipe with the smaller, second face of the gasket being closer to the spigot end than the larger, first face of the gasket. The gland fitting has a plurality of apertures for receiving standard bolts. The gland fitting also has an integrally formed, protruding lip, which encircles the face of the gland fitting at its inside diameter, such that the lip is adjacent to the surface of the pipe and faces the spigot end of the pipe when the gland fitting is positioned on the pipe. The face of the flanged portion has a tapered notch designed to receive the conically shaped gasket when the spigot end is inserted into the bell. The joint is formed when the spigot is axially inserted into the bell, and the gland fitting and the flanged portion are bolted together, causing the lip of the gland fitting to compress the gasket thus sealing the two pipe pieces.
Push-on joints and mechanical joints, have an increased tendency to loosen after a lengthy period of use, especially when repeatedly placed under large bending forces. Thus, a need also exists for a fluid connector assembly that can withstand strong bending forces caused by riser movement for extended periods. A new fluid connector assembly is needed that can be used with standard pipe or pressure vessels, can be assembled easily in the field, and can be equally or more stable and secure than other alternatives now available.
The disadvantages of the prior art are overcome by the present invention, which meets all of these needs. An improved closure assembly and a method of closing a hub attached to a pipe, a pressure vessel, or other container are hereinafter disclosed.